Power control is required in most power amplifier applications. This is typically accomplished through the use of power control actuation circuits between the power supply and the power amplifier core, such as a two level push-pull P and N amplifier configuration. For different power levels, the top and bottom amplifying entities will experience different dc and ac signal levels as a function of the power control voltage. These ac and dc signal levels must be carefully controlled to avoid potentially damaging voltage levels.
By adjusting the voltage drop across the power control actuation circuits, the power supply voltage to the power amplifier core can be varied accordingly. While the power control actuation circuits can be provided with a low on-resistance to reduce the power loss on it, such devices are typically large and use more surface area of an integrated circuit. Large device size can results in a large parasitic capacitance, which can also result in a higher substrate loss if there is also a large voltage swing and high frequency on the power control actuation circuits node. Large device size can also induce undesirable harmonic distortion, among other things.